[Limited time Q&A event No. 3] 007 (Ended) (3 Haiyou winners +40 wealth)

Process material and public material pipelines should be equipped with shut-off valves at the device boundary (usually inside the device boundary), with the following exceptions:: a) Exhaust system b) Drain pipe when emergency drain tank is located outside the boundary ； If valves must be installed in these two situations, lead seal opening (CSO) is also required. c) Material pipes that will not cause material leakage or accidents. d) Material pipes that do not require measurement.

Utility pipelines that can be opened and shut down at the same time as the device, such as: Clean air ducts, nitrogen ducts, circulating water ducts, fresh water ducts, steam ducts, etc. do not need to be equipped with cut-off valves ； Material pipelines that supply separate devices, pipelines that already have shut-off valves in the tank area and the device, such as: Raw material pipelines, product pipelines, etc. do not need to be equipped with cut-off valves ；

1. When used as a combined device (same start and stop at the same time), the pipeline between the two devices does not need to be equipped with a cut-off valve； 2. Process material pipelines that are supplied separately do not need to be equipped with cut-off valves. ； 3. When the buffer tank for public materials (air, nitrogen, steam) is close to the inlet and outlet of the device and has a valve to cut off, the cut-off valve does not need to be installed.

Basically the same view on the first floor. However, now domestic accident discharge systems also have the phenomenon of setting long-open cut-off valves in front of the safety valves. It may be because they are worried about the quality of the safety valves on the discharge pipes. Moreover, the cut-off valves are installed to facilitate the maintenance of the safety valves. This post was last edited by tekchina on 2009-4-16 18:01 ]

Agree with the 1st floor, this question is a regulation and cannot be used 1 Application scope 1.0.1 This regulation applies to the chemical process system major. The valves mentioned do not include safety valves, steam traps, sampling valves, pressure reducing valves, etc., but include the setting of restricting orifice plates, blind plates and other pipe fittings that have similar functions to valves. Shut-off valves are used as the general term for these valve parts. The function of the cut-off valve is to cut off the fluid or change the flow direction of the fluid. It should be set according to the requirements of production (including normal production, start-up and shutdown, and special working conditions), maintenance and safety, and economic rationality should also be considered. 1.0.2 Valve setup and selection of appropriate category (not model). Valves are an important task for process system professionals when preparing PI diagrams. The content described in this regulation takes into account the general requirements for production and safety. When system majors conduct engineering design with reference to these regulations, they should make choices based on the specific conditions of the project, local meteorological conditions, inter-factory collaboration, device operation requirements, fluid characteristics, user's special requirements and economy, etc. 1.0.3 This regulation comprehensively introduces the valve settings for the listed situations and the detailed requirements of various chemical units. Please refer to the basic unit model of the PI diagram of the corresponding unit. 1.0.4 This regulation also introduces the characteristics of general industrial valves and factors to be considered when selecting valves in engineering design. 2 Valve settings 2.0.1 Valve settings at the boundary 2.0.1.1 Process material and public material pipelines should be equipped with shut-off valves at the device boundary (usually inside the device boundary), with the following exceptions:: (1) Exhaust system. (2) Discharge pipe when the emergency discharge tank is located outside the boundary ； In these two situations, if a valve must be installed, the lead seal must also be opened ( C.S.O ). (3) Material pipes that will not cause material stringing or accidents. (4) Material pipes that do not require measurement. 2.0.1.2 The valve settings at the boundary are shown in several ways as shown in Figure 2.0.1. Among them (1) is suitable for cutting general materials ； In places where material leakage may cause explosions, fires and other safety accidents or important product quality accidents, in order to prevent internal leakage of the valve, use (2), (4) and (5) in Figure 2.0.1 to add blind plates ； (3) and (5) in Figure 2.0.1 are suitable for situations where the line needs to be swept upstream or downstream after feeding. Valve C can be used for purging, draining, and checking leaks. The measuring instrument can also be installed between two valves in series. (5) in Figure 2.0.1 is suitable for places where pressure changes may be large, and the check valve can act as an instant cut-off. 2.0.2 Setting of root valve 2.0.2.1 When a medium needs to be transported to multiple users, in order to facilitate maintenance or save energy and prevent freezing, in addition to installing a cut-off valve near the equipment, a cut-off valve called a root valve is installed on the branch pipe close to the main pipe. Usually used in public material systems (such as steam, compressed air, nitrogen, etc.). When a process material is routed to multiple users (e.g. solvent), the same settings are required. The valve shown in Figure 2.O.2 is the root valve. When there are requirements such as energy saving and antifreeze, the distance between the root valve and the main pipe should be as small as possible. 2.0.2.2 Root valves should be installed on all branch pipes of public material pipelines in chemical installations to prevent the installation or the entire plant from shutting down due to damage to individual valves. 2.0.2.3 Steam and overhead water pipes. Even if it only leads to one device or piece of equipment, when the branch pipe exceeds a certain length, it is necessary to add a root valve to reduce the dead zone, reduce energy consumption, and prevent freezing. 2.0.2.4 For two or more steam equipment that are mutually backup, it should be determined whether to install branch pipe root valves respectively according to their importance in production. 2.0.2.5 The root valve of the common material branch pipe is set by the pipeline professional during the pipeline layout design. The process system professional needs to review whether the branch is appropriate and display the root valve on the common material PI diagram (distribution diagram).

To add to the content on the 6th floor, this is the content specified in HG/T20570.18-95 "Valve Settings". It’s in this forum! Personally think: The pipelines between combined devices that must be started and stopped at the same time do not need to be equipped with boundary valves. The emergency discharge pipeline is not equipped with boundary valves. However, in most cases we still need to set boundary valves. This is an issue that should be considered in our design.

a) Exhaust system b) Drain pipe when emergency drain tank is located outside the boundary； If valves must be installed in these two situations, lead seal opening (CSO) is also required. c) Material pipes that will not cause material leakage or accidents. d) Material pipes that do not require measurement. e) There is no need to vent the pipeline

Three additional points: 1. If the material return device will be affected, a boundary valve must be installed respectively. When stopping, close the cut-off valves of both boundary devices at the same time to close the material in the device. 2. Boundary valves cannot be installed in material pipes that are prone to sedimentation. When the machine stops abnormally, the material must be drained from the set drain valve to prevent blockage. 3. Boundary valves should be installed on dangerous devices such as gas cabinets. Because the consequences of an accident involving an ultra-high level in the gas tank will be disastrous, boundary valves should be installed at the inlet and outlet of the gas tank.

1. Sewage recovery pipelines, including domestic sewage, rainwater, etc. 2. Exhaust system. 3. Discharge pipe when the emergency discharge tank is located outside the boundary ； In these two situations, if a valve must be installed, the lead seal must also be opened ( C.S.O ). 4. For some material pipes that will not cause material leakage or accidents, sometimes it is necessary to cut without boundaries. 5. Material pipes that do not require measurement.